The invention relates to an osteochondral plug graft instrument, kit and method. More particularly, the invention relates to an instrument to harvest an osteochondral plug graft for implant in osteochondral tissue in need of repair. Also, the invention relates to a kit including the instrument and to a method to use the instrument.
Human joint surfaces are covered by articular cartilage that provides a resilient, durable surface with low friction. Cartilage is an avascular tissue that has a small number of chondrocytes encapsulated within an extensive extracellular matrix. The cartilage acts to distribute mechanical forces and to protect subchondral bone. The knee is a particular instance of a cartilage surfaced (the condyle) bone area. The knee comprises three bones—the femur, tibia, and patella that are held in place by various ligaments. Corresponding chondral areas of the femur and the tibia form a hinge joint and the patella protects the joint. Portions of the chondral areas as well as the underside of the patella are covered with an articular cartilage that allows the femur and the tibia to smoothly glide against each other without causing damage.
Damage to the articular cartilage, subchondral bone or both can result from traumatic injury or a disease state. For example, articular cartilage in the knee can tear due to traumatic injury as with athletes and degenerative processes as with older patients. The knee cartilage does not heal well due to lack of nerves, blood vessels and a lymphatic system. Hyaline cartilage in particular has a limited capacity for repair and lesions in this material without intervention, can form repair tissue lacking the biomechanical properties of normal cartilage.
A number of procedures are used to treat damaged articular cartilage. Currently, the most widely used procedure involves lavage, arthroscopic debridement and repair stimulation. Repair stimulation is conducted by drilling, abrasion arthroplasty or microfracture. The goal of this procedure is to penetrate into subchondral bone to induce bleeding and fibrin clot formation. This promotes initial repair. However, the resulting formed tissue is often fibrous in nature and lacks the durability of normal cartilage.
Osteochondral grafting has been used to repair chondral damage and to replace damaged articular cartilage and subchondral bone. In one such procedure, cartilage and bone tissue of a defect site are removed by routing to create a bore of a precise cylindrical geometry. Then a cylindrical cartilage and subchondral bone plug graft is harvested in a matching geometry. The harvest is typically from another body region of less strain. The plug graft can be harvested from a recipient source (autograft) or from another suitable human or other animal donor (allograft). The harvested plug graft is then implanted into the bore of the routed defect site. Healing of the graft bone to host bone results in fixation of the plug graft to surrounding host region.
Surface and other configuration characteristics of a plug graft are critical to achieving a successful implant. The surface of the transplanted graft must have the same contour as the excised osteochondral tissue. If the contour is not a correct match, a repaired articular surface is at risk for further damage. Also, the configuration of the plug graft must conform to a configuration of the recipient socket. Otherwise, a transplanted graft will be unstable and will move causing complications to the recipient area. Instability and movement result in poor integration of the plug graft with surrounding host tissue.
Instruments have been developed for harvest of plug grafts and for insertion for repair of a recipient patient's osteochondral tissue. These instruments can be unstable and difficult to control when the instruments are operated to harvest from a non uniform surface site such as a femoral trochlear groove. When activated in such areas, vibration can cause the instrument to “wander,” meaning that the instrument strays along a site surface in varying cutting postures. Once the bit of the instrument wanders off-course, it is difficult to bring it back on center. The wander of the instrument makes it impossible to harvest a perpendicular and smooth walled plug graft from such sites.
There is a need for an instrument and method to harvest a perpendicular and smooth walled plug graft to avoid post implantation motion, graft surface mismatch and host tissue integration failure. There is a need for a kit to provide a surgeon with an instrument to harvest a normal configured plug graft for normal implant in a patient osteochondral tissue in need of repair.